Gelam tree-derived carbon nanosheets as thick and freestanding electrode for supercapacitor

Abstract

Most electrodes for supercapacitors are prepared as thick layer electrodes. Compact, thick and free-standing electrodes are needed for supercapacitor with high volumetric capacitance and energy density. Carbon nanosheets were obtained from treating the bark of the Gelam tree (Melaleuca cajuput Powell) via hydrothermal and microwave processes. The XRD results showed the presence of graphitic carbon in the Gelam tree-derived carbon nanosheet. The carbon nanosheet (the thickness of 0.01 cm) was mixed with graphite and poly(aniline) as conducting binder to fabricate a supercapacitor electrode. Conductivity as high as 3.67 x 10-2 S cm-1 were obtained from the electrode using the carbon nanosheet to graphite the ratio of 3:7. The electrode with this composition had a porous structure. The electrode with a carbon nanosheet to graphite the ratio of 7:3 had a granular morphology with a low conductivity of 0.8 x 10-3 S cm-1. Cyclic voltammetry tests were conducted in lithium chloride and ammonium cyanate-based electrolytes. Both types of electrodes (ratio 3:7 and 7:3) had the same trend of capacitance and voltage window in lithium chloride and ammonium cyanate-based electrolytes. Capacitance as high as 0.0618 F was obtained from the electrode using the 7:3 ratios nanosheet in 10 % ammonium cyanate electrolyte. A novel supercapacitor with high capacitance designed using a thick layer electrode can readily be prepared from the carbon nanosheets derived from the agricultural wood waste.